We won't be running into Marvin or any Biker Mice, but life on Mars may still be found in the form of microbes. As the search moves further underground with projects like ExoLance, researchers at the University of Texas at Austin have found another promising place to look: a strange formation that could be the remains of an ancient "ice cauldron" that would have provided a warm, chemical-rich, life-friendly environment.

The funnel-shaped depression is located inside a crater in the Hellas basin. The region is believed to have hosted a giant lake at some point in the Red Planet's past, and features of the landscape suggest it was rich in both glaciers and volcanic activity. It is the interaction between ice and lava that could make the area prime real estate for microbial life.

"We were drawn to this site because it looked like it could host some of the key ingredients for habitability – water, heat and nutrients," says Joseph Levy, lead author of the study.

Levy first spotted the landmarks in Hellas basin and another in the Galaxias Fossae region in 2009, in pictures taken by the Mars Reconnaissance Orbiter (MRO). He noted their similarity to Earthly structures called ice cauldrons, which are created when volcanic eruptions take place underneath ice sheets. The MRO has previously found evidence of these in the Sisyphi Montes region of Mars.

"These landforms caught our eye because they're weird looking," says Levy. "They're concentrically fractured so they look like a bulls-eye. That can be a very diagnostic pattern you see in Earth materials."

To determine if the Hellas and Galaxias Fossae formations are ice cauldrons or just asteroid impact sites, the team used stereoscopic images to create digital elevation models in 3D and found that both were distinctly funnel-shaped.

"That surprised us and led to a lot of thinking about whether it meant there was melting concentrated in the center that removed ice and allowed stuff to pour in from the sides," says Levy. "Or if you had an impact crater, did you start with a much smaller crater in the past, and by sublimating away ice, you've expanded the apparent size of the crater."

The funnel-shaped structure in the Hellas region, as seen from several different angles, might be a good place to search for microscopic Martian life(Credit: Joseph Levy/NASA)

But despite their similar appearance, the team determined that the two landmarks probably represented one from each column. Galaxias Fossae appears to be an impact site, due to the apparent presence of debris around it that would've been kicked up by an asteroid colliding with the surface. On the other hand, the Hellas funnel doesn't have a debris field, and the pattern of its fractures is consistent with a subglacial eruption melting ice away.

An event like that would've led to life-favoring conditions with liquid water, nutrients and heat, the team says, making the Hellas depression a prime location for future Mars missions. Even Galaxias Fossae may warrant a closer look, since it can't be ruled out that it isn't also an ancient ice cauldron.

The research was published in the journal Icarus.

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